The present disclosure relates to an electrolytic solution including a solvent, and a battery using the electrolytic solution.
In recent years, portable electronic devices such as camera-integrated VTRs (videotape recorders), cellular phones, or laptop computers are widely used, and size and weight reduction in the portable electronic devices and an increase in longevity of the portable electronic devices have been strongly demanded. Accordingly, as power sources for the portable electronic devices, the development of batteries, specifically lightweight secondary batteries capable of obtaining a high energy density have been promoted.
Among them, a secondary battery (a so-called lithium-ion secondary battery) using insertion and extraction of lithium for charge-discharge reaction, a secondary battery (so-called lithium metal secondary battery) using precipitation and dissolution of lithium, or the like holds great promise, because the secondary batteries are capable of obtaining a large energy density, compared to a lead-acid battery or a nickel-cadmium battery.
As an electrolytic solution for the secondary batteries, a combination of a carbonate-based solvent such as propylene carbonate or diethyl carbonate and an electrolyte salt such as lithium hexafluorophosphate is widely used (for example, refer to Japanese Patent No. 3294400). It is because the combination has high conductivity, and its potential is stable.
In addition, regarding the composition of an electrolytic solution, to improve cycle characteristics, storage characteristics and the like, techniques of including various sulfone compounds in an electrolytic solution have been proposed. As the sulfone compounds, a compound having a sulfonyl fluoride type structure (for example, refer to Japanese Unexamined Patent Application Publication Nos. 2002-359001, 2006-049112, 2006-049152 and 2006-294519), disulfonic anhydrides (for example, refer to Japanese Unexamined Patent Application Publication Nos. 2004-022336 and 2006-344391 and Japanese Patent No. 3760539), disulfonate derivatives (for example, refer to Japanese Unexamined Patent Application Publication Nos. 2000-133304, 2006-3513337 and 2007-080620) and the like are used.
In recent years, as portable electronic devices have higher performance and more functions, the power consumption of the portable electronic devices tends to increase. Accordingly, secondary batteries used in the portable electronic devices are frequently charged and discharged, thereby the cycle characteristics of the secondary batteries easily decline. Moreover, the portable electronic devices are widely used in various fields, and there is a possibility that the secondary batteries are exposed to a high-temperature atmosphere during transport, in use or during carrying, so the storage characteristics of the secondary batteries also decline easily. Further, in the case where a secondary battery includes a film-shaped package member, when the secondary battery is exposed to a high-temperature atmosphere, the secondary battery is easily swelled, so swelling characteristics are also important. Therefore, further improvement in battery characteristics such as cycle characteristics, storage characteristics and swelling characteristics of the secondary batteries is desired.
In view of the foregoing, it is desirable to provide an electrolytic solution and a battery which are capable of improving battery characteristics.